Marty at aimClear posted his Facebook SEO Ranking Factors, 2010 Study Results, which he presented at SMX Advanced just a month or so ago.
A Sphinn thread has discussion around the study. Let me summarize the key points:
Marty goes through how Facebook search suggestions and how to leverage those suggestions to your benefit. He then describes how Facebook ranks their results, and the most important factors for that ranking. He moves on to Facebook pages and how to help those pages rank well. Then there are Facebook Group pages, App pages and event pages for ranking.
If you are interested in how Facebook search works and ranks, check out Marty's post.
Forum discussion at Sphinn.